How Long Does It Take for the Smell to Go Away After Replacing the Catalytic Converter?
3 Answers
After replacing the catalytic converter, the smell usually disappears within a week. The catalytic converter is an essential external purification device in the automobile exhaust system. Its function is to convert harmful gases such as carbon monoxide, hydrocarbons, and nitrogen oxides from vehicle exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. The catalytic converter consists of a shell, a damping layer, a substrate, and a catalyst coating. The reasons for catalytic converter failure include: 1. Prolonged idling; 2. Delayed ignition timing; 3. Overly rich fuel mixture; 4. Engine oil burning; 5. Oxygen sensor failure; 6. Overheating due to incomplete cooling; 7. Switch cut-off while driving.
After I replaced the catalytic converter last time, that foul smell disappeared, but there's still a slight sulfur odor during the first few minutes of starting the car, which is unpleasant. Typically, with a new converter installed, the smell noticeably reduces after about ten minutes of driving because the catalytic converter needs to warm up to its operating temperature to efficiently process exhaust gases. You should let the car idle for a short while before driving, allowing the exhaust temperature to rise, and the smell will dissipate faster. I once helped a friend fix his car and encountered a case where the smell didn't disappear immediately after installation. Upon inspection, we found that the mounting bolts weren't tightened properly, causing a leak, so it's crucial to ensure a good seal during installation. Additionally, fuel quality matters—after installing a new catalytic converter, it's best to use high-quality gasoline to minimize impurities. If the smell remains unbearably strong after driving, take it to a professional shop immediately to check for other potential issues, like a faulty oxygen sensor. In short, be patient and wait a few minutes—in most cases, the smell will go away. Safety first!
I've been driving an old car for over ten years and have replaced the catalytic converter two or three times. Each time after replacement, I immediately tested for changes in odor. The first time I replaced it, I thought the bad smell would disappear instantly, but I was a bit disappointed to still notice a slight odd smell for the first few minutes after starting the car. Later, the mechanic explained that the catalytic converter needs to heat up before it becomes effective. Typically, after driving for a while, about five to ten minutes, the smell mostly fades. He advised not to rush into long trips after replacement but to test drive nearby first, checking for leaks in the exhaust system, such as loose connections at the exhaust pipe joints. Additionally, the quality of the catalytic converter itself affects the time it takes—genuine parts may work faster, while inferior ones may take longer. I make it a habit to regularly clean the throttle body to keep the system running smoothly and avoid subsequent issues. If the bad smell persists after a day, don’t delay—head straight to the repair shop, as it could be due to improper installation or poor electrical connections. In short, most people see improvement within ten minutes.
